P728: GENE EXPRESSION PROFILE REVELS T-LYMPHOCYTES ACTIVATION THROUGH CELL CYCLE PROGRESSION AND MITOCHONDRIAL METABOLISM REGULATION IN MYELODYSPLASTIC SYNDROMES WITH DEL(5Q) AFTER LENALIDOMIDE TREATMENT
Authors: M. del Rey, L. A. Corchete, T. González, F. López-Cadenas, E. Lumbreras, S. M. Toribio, B. Xicoy, J. Sánchez-García, T. Bernal, G. F. Sanz, P. Fenaux, J. M. Hernández-Rivas, M. Diez-Campelo
Journal: HemaSphere (2022)

Background: Lenalidomide is a potent drug whose mechanisms of action in del(5q) clone from Myelodysplastic Syndromes (MDS) have been extensively described. Lenalidomide also induces immune modulation independent of del(5q) and has multiple effects on T-cell signaling; however, the molecular and cellular determinants that mediate this immunomodulatory function remain elusive. Aims: To better understand the immunomodulatory activity of lenalidomide in MDS patients with del(5q) by in vivo sequential gene expression profile studies of T lymphocytes in response to the treatment. Methods: Our study was conducted in patients included in the Sintra-REV Clinical Trial (phase III). Sequential study was carried out in 26 samples from 13 paired patients. Seven out 13 were treated with lenalidomide and achieved a major erythroid and cytogenetic response. Peripheral blood (PB) samples were collected before and one month after treatment in treated patients and at the same time points for non-treated patients. CD3+ cells were collected from PB samples and total RNA was isolated. SureSelect Strand Specific RNA library (Agilent Technologies) was applied to study changes in RNA levels. Raw reads were aligned against the Human genome GRCh37 using the STAR aligner. Counts were assigned to Ensembl gene IDs through HTseq using its UNION version. Differential gene expression was determined with DESeq2, considering as statistically significant those genes with FDR < 0.05. Pathway over-representation analysis (ORA) was conducted in the Webgestalt suite. Results: 332 genes were differentially expressed in CD3+ lymphocytes one month after lenalidomide treatment in our cohort of patients; of note, none of them were observed after one month in non-treated patients. The ORA revealed significant differences in the gene expression profile of sixteen cytokines (e.g. IL10, TNFSF10, IFNG, IL6 and MBP6). These genes could contribute to activation of an antileukemic immune response, help to correct the anemia as well as attenuate inflammation signaling in MDS patients with del(5q). The ORA also showed an enrichment of genes involved in cell cycle (35 genes). The most represented up-regulated genes related to this pathway were: cyclines (CCNB1, CCNB2, CDK1), centromere genes (CENPE, CENPM, CENPU), kinesin family members (KIF18A, KIF23, KIF2C) and genes involved in cell division (CDC6, CDC7, CDC25A). It has been described that lenalidomide inhibits CDC25A selectively in the del(5q) clone resulting in G2/M arrest and apoptosis. By contrast, our study showed that this gene was upregulated in T-lymphocytes promoting cell cycle and proliferation of these cells. In addition, 456 genes were differentially expressed between non-treated and lenalidomide treated samples; 30 of them were related to mitochondrial metabolism (e.g HIBCH, ECHS1, DECR1, ACSM1, HADH, COQ3, COQ5, SDHAF3, SDHAF4) and mitochondrial translation (e.g. MRPL15, MRPL24, MRPL48, MRPL51, MRPS33). Thereby, T lymphocytes adaptive responses as well as sustained killing by cytotoxic T cells could be mediated by mitochondria in treated patients. Summary/Conclusion: To our knowledge, this is the first report describing RNA expression profiles in PB CD3+ lymphocytes collected from lenalidomide-treated del(5q) patients, contributing to overall understanding of lenalidomide action. A better understanding of the molecular targets that mediate the immunomodulatory activity is needed to harness the full potential of this agent. Functional experiments trying to test the new biological mechanisms described above are currently conducted.